//
// Filter
//
.filter-gray
  -webkit-filter: grayscale(100%);
  -moz-filter: grayscale(100%);
  -o-filter: grayscale(100%);
  filter: grayscale(100%);
  filter: gray;


support-for-ie ?= true
opacity(n)
  opacity: n
  if support-for-ie
    filter: unquote('progid:DXImageTransform.Microsoft.Alpha(Opacity=' + round(n * 100) + ')')